This invention relates generally to fire event sensing devices and, more particularly, to a system for verifying and improving the accuracy of detection of fire events by fire detection devices that utilize multiple fire event sensors so as to reduce false alarms.
Various devices are known in the art which utilize more than one air condition sensor for sensing predetermined ambient air conditions indicative of a fire event. Although assumably effective for their intended purposes, existing fire event detection devices frequently sound false alarms. An ambient air condition sufficient to activate an alarm may, in fact, be caused by some event other than a fire. Therefore, existing devices often erroneously energize an alarm when a true fire event does not exist.
Therefore, it is desirable to have a system for use with multi-sensor fire detection systems that reduces the threshold parameters of other sensors when a first sensor supposedly indicates a fire event and then energizes an alarm only if the fire event is verified by more than one sensor. Further, it is desirable to have a system that modifies predetermined threshold parameters if sensed air conditions at initial power-up indicate a likelihood of a climate-induced false alarm unless the parameters are modified.
A system for verifying and improving the accuracy of detection of a fire event by fire detection devices utilizing multiple air condition sensors includes a programmable logic circuit having a plurality of predetermined threshold parameters. Each threshold parameter corresponds to a respective air condition sensor in the fire detection device and includes a data type corresponding to the data type of an ambient air measurement taken by a respective sensor. The logic circuit compares input data received from the air condition sensors with the predetermined parameters. If this comparison reveals that data from a particular sensor satisfies a corresponding threshold parameter, the circuit decreases the levels of the other threshold parameters other than the parameter corresponding to the particular sensor. The circuit also increases the frequency with which all of the sensors are sampled. Then, if data from the sensors satisfies the corresponding threshold parameter as well as at least one of the decreased threshold parameters, the logic circuit energizes an alarm. Therefore, decreasing the other parameters and making another data comparison causes a quick verification that a true fire event had been sensed by the first sensor and avoids possible false alarms.
Further, the logic circuit compares data from the air condition sensors at initial power-up to the predetermined threshold parameters and modifies appropriate parameters that appear likely to cause a false alarm. In other words, if an ambient air condition almost satisfies (or even exceeds) a corresponding parameter at power-up, then an erroneous alarm activation is likely based solely on a normal environmental condition. For example, a fire detection device may include an air condition sensor that senses temperature and which corresponds to a threshold parameter of, say, 135xc2x0 F. If the sensor indicates at power-up that the ambient air temperature is already 127xc2x0 F., then the logic circuit may determine that the threshold parameter should be raised by a predetermined amount so as to avoid a false alarm (which would occur in this example if the temperature increased to 135xc2x0 F., e.g., in a hot attic in the summertime). Therefore, the logic circuit is able to adapt the sensors to the environment at power-up so as to reduce the incidence of false alarm and, thus, verify the accuracy of a detection of a fire event prior to sounding an alarm.
Therefore, a general object of this invention is to provide a system for verifying detection of a fire event by a fire detection device that utilizes more than one air condition sensor.
Another object of this invention is to provide a system, as aforesaid, that decreases the threshold parameters corresponding to other sensors if a particular threshold parameter is satisfied by input data received from the sensors.
Still another object of this invention is to provide a system, as aforesaid, that energizes an alarm if the data from the sensors satisfies both the threshold parameter corresponding to the particular sensor and at least one decreased parameter.
Yet another object of this invention is to provide a system, as aforesaid, in which an alarm is immediately activated if data from the sensors satisfies at least two corresponding threshold parameters.
A further object of this invention is to provide a system, as aforesaid, which modifies appropriate threshold parameters if initial input data received by the logic circuit at power-up indicates the likelihood of a false alarm due to environmental conditions.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention.